Conference terri::cars_uk

    
    If somebody comes up with and answer to .0 question, then I'd be just
    as glad to know who's computer runs that lot? On Tuesday every London
    Radio station was on about the power failure and Traffic light
    distruption, they also mentioned computer failure but didn't say what
    the makers name was... Why is it everytime it's a Digital system
    failure everyone gets to here the name??
    
    Ta
    
    - Ian

	All traffic lights used to be stand alone systems that
	ticked away (literally, they used electro-mechanical controls)
	by themselves. Most still do work just like this though I dare
	say they've got electronics now.

	But then they started to think it would be a good idea to link
	them together such that traffic travelling at a constant speed
	ie 25-30 mph would flow unobstructed. I used to live near Slough
	and the lights there were possibly the first to be done this way
	by way of some experiment. They used to have signs saying "Linked
	Lights" along the Bath Road. Unfortunately, for the designers of
	the system, it was realised by some unscrupulous users that if
	you went very quickly you could also whizz through the entire
	set without being held up!.

	Some traffic lights have traffic sensors associated with them.
	These used to be rubber inserts in the road, and the unscrupulous
	kids in our area delighted in trying to make the lights change by 
	jumping on them, when of course there was no traffic.

	Nowadays many towns have computer controlled lights, and I think
	that the London one is in Scotland Yard.

	-John

there's a set of lights on a road leading out of coventry that stop you leaving
the city UNLESS another car enters the city (from the opposite direction)!

end up with a fairly long wait sometimes...


...art

Re .3; doesn't sound like a sensible way to reduce inner city congestion!

Re .1; I think GEC make a lot of traffic lights and controllers.  Try looking
on the control boxes at the side of the road by traffic lights and see whose
name is on them.  (The control boxes are about 4 feet high, 2 feet wide, 1 foot
deep and mid grey in colour.  Well, the ones I've seen are...)

Scott

    Don't you know of the great traffic light scam?
    
    This consisted of convincing local authorities that temporary traffic
    lights would be much less disruptive if they could detect traffic
    approaching them and change to allow the traffic to pass without delay.
    "All you need", they said "is to fit out radar detector on top of each
    set of lights and then it will all be automatic". They then sold lots
    of empty black boxes together with rolls of double sided sticky tape
    for thousands of pounds a time. This is why most temporary lights now
    have little boxes on top of them, and you still get to wait when
    there's nothing comming the other way.
    
    BTW, it's rumoured that this was done by the same team that sold
    millions of plastic cones to local authorities, having convinced them
    that blocking off one lane of a dual carriageway that needed no
    repairs, would save wear on that side of the road and hence prevent the
    disruption caused when they would have had to block it off to repair it
    at a later date.
    
    Peter

Re: .0

The highway authority is responsible for traffic signals.  In some cases
they have arrangements with police to assist in controlling the lights.

Re: .6

There is I believe a legal maximum time that a red light can be shown.
The biggest problem with temporary lights is setting the all red period.
If it is too short chaos results, so it is usually set long enough so
that in worst case conditions vehicles passing a green light will get
past the single lane section plus a few yards.

jb

    When I was at University in London, 10 years ago now, I remember reports
    to the effect that Most of the Traffic lights were centrally
    controlled by computer, but had no 'feedback' as to the amount of
    traffic. However things were made better by the fact that some
    intelligence was built in, in that there were differences in timing
    at different times of day.
    
    Then they decided that they really ought to have some feedback as to
    how much traffic there was.
    
    I seem to remember for many weeks, reports of traffic holdups because
    of 'slot cutting'.
    
    Graham

         Morecambe (Lancs) on 'The Sunset Coast' has traffic lights. These 
         have proven very popular with the mainly elderly population, and 
         therefore Lancaster City Council have built a stadium around 
         several sets of these lights at Bare, between Lancaster and 
         Morecambe.
         
         jb. (It's Friday!)

.3

>there's a set of lights on a road leading out of coventry that stop you leaving
>the city UNLESS another car enters the city (from the opposite direction)!

Is this why there's always a demand to "Send people to Coventry". Often
wondered what the origin of this expression was but now it's clear. Those
already there want to get out!.

-John

    Its some time ago that I had anything to do with traffic in London and
    its regulation but. The lights used to be a bit of both , computer
    controlled and self running. The memory is a bit faded but the computer
    controlled ones were controlled from NSY and were on lights in key
    traffic black spots. I guess that the number of traffic black spots has
    changed so the number of controlled lights has changed. As for who's
    computer???? I suspect it would have been someone like ICL back in them
    days as most of the police national computer facility was that or IBM.
    
    Whatever, you can tell that its computer controlled. They say that "
    to really foul things up you need a computer" What more can you say.
    
    
    Garry

Re: .11

>								As for who's
>    computer???? I suspect it would have been someone like ICL back in them
>    days as most of the police national computer facility was that or IBM.
    
I would take a small bet that the traffic signals were controlled by a
Ferranti computer.   The Police National Computer is a Burroughs (now
Unisys) system.  It is being replaced by a Siemens system.

jb

    The traffic lights in Belfast (and according to the Belfast control
    centre in quite a few cities in the UK) are computer controlled.
    They work by detecting traffic flow by means of detection loops
    in the road and adjust light timings accordingly. Most of these
    systems are Plessey or GEC systems driven by either PDP11s or
    Microvaxes. The Belfast system was origionally installed in 1978
    and consisted of 3 PDP1134s running RSX.
    

     Sydney has an extensive set of computer controlled traffic lights.
    They are powered by various PDP11's, big Vaxes, and multiple
    MicroVaxes. We supply various maintenance services for them.
    Regards, Ray